Liquid fuel-fired grille

ABSTRACT

A cooking surface or grille heated uniformly by the products of combustion from a liquid fuel-fired burner, wherein the products of combustion are caused to flow beneath the cooking surface of the grille through inverted V-shaped channels which define gastight passageways that extend from the back to the front of the grille and in the opposite direction through adjacent V-shaped gas-tight channels alternating with the inverted V-shaped channels to provide an efficient and uniform transfer of heat energy from the combustion gases to the cooking surface of the grille.

0 United States Patent 1191 1111 3,837,329

Mutchler Sept. 24, 1974 [5 LIQUID FUEL-FIRED GRILLE 3,525,325 8/1970Perl 126/39 J [75] Inventor: [131:] A. Mutchler, University City,Primary Examiner wimam F. O,Dea

' Assistant Examiner-Harold Joyce [73] Assignee: The United States ofAmerica as Attorney, Agent, or Firm-Eugene E. Stevens, III;

represented by the Secretary of the Herbert Berl; Lawrence E. LabadiniArmy, Washington, DC. 22 Filed: July 5,1973 L k ff Z d I b h coo mg suace or gn e eate um ormy y t e [2]] Appl- 376,662 products of combustionfrom a liquid fuel-fired burner, wherein the products of combustion are[52] U.S. Cl. 126/44, 126/39 J caused to flow at t ooking surface of the[51] Int. Cl. F24c 3/06 grille through inverted P Channels which [58]Field of Search 126/44, 19.5, 39 J, 39 H, fine g g p g y that extendfrom the back 12 39 N, 39 K, 391 to the front of the grille and in theopposite direction through adjacent V-shaped gas-tight channelsalternat- 5 R m- Cited ing with the inverted V-shaped channels toprovide an UNITED STATES PATENTS efficient and uniform transfer of heatenergy from the combustion gases to the cooking surface of the grille.252,307 l/1882 Fagan 126/44 I 1 3,408,999 ll/1968 Mutchler 126/44 7Claims, 3 Drawing Figures fl o 2 I '1' 11 g 1 37 1 III/HI 1 [4 20 l I JI 1 I I 1 1 *1 /L: I I I II I I I i] I9 I II I I0 I; .H I ily l lil 7 3'I I 23 /;L/\ 1 1 11 I I8 il- I7 I I, l- I 1] l/ 1'1 i x: 71 14 I "/i l I1 I I I I t l I I 1 I) i ii. I i l I, l2

PAYENTEUSEPZMSH smut III III FIG.

PAIENIEU 2 74 SHEET 2!! 2 LIQUID FUEL-FIRED GRILLE The inventiondescribed herein may be manufac tured, used and licensed by or for theGovernment for governmental purposes without the payment to me of anyroyalty thereon.

BACKGROUND OF THE INVENTION This invention relates to cooking equipmentand, more particularly, to a cooking surface or grille heated by thecombustion gases from a liquid fuel-fired burner.

Many different types of heating arrangements for cooking surfaces orgrilles are known in the art wherein either a portion of the surface orsubstantially all of the surface is exposed to a source of thermalenergy, as for example, by the direct application of flames from gasburners or the conduction of heat from electrical resistance coils. Evenwith cooking surfaces constructed of highly conductive materials,localized hot spots and uneven heating over the surface is a commonproblem in the art. It is recognized that the maintenance of an evenlyheated cooking surface is highly desirable insofar as this willfacilitate the production of uniformly cooked food items. A cookingsurface having a uniform temperature throughout is difficult to achieveespecially when the source of thermal energy is combustion gas from aliquid fuel-fired source since it has proven to be virtually impossibleto effect an efficient and uniform heat exchange from the hot gas to thecooking surface. One such attempt to uniformly heat'a cooking surfaceusing a special combustion gas distribution arrangement is described inUS. Pat. No. 3,408,999 which issued to Paul A. Mutchler on Nov. 5, 1968wherein the combustion gases are first caused to flow around and beneaththe peripheral edges of the cooking surface so that the heat will flowfrom the peripheral edge toward the center of the surface. It is obviousthat even with such an arrangement, the temperature at the periphery ofthe cooking surface will tend to be higher than at the center and thatthe heat exchange occurring within the relatively large chambers beneaththe cooking surface will be somewhat inefficient due to the inability toprecisely control the turbulence and flow of gases therein. Theinvention described herein provides a more precise control on both thedirection or location and the quantum of the gas streams and produces ahighly turbulent stream which more efficiently gives up heat to the heatexchange surface than does a less turbulent gas stream.

SUMMARY OF THE INVENTION The present invention is concerned with acooking surface or grille heated by the flow of hot combustion gaseswhich employs a novel arrangement for transferring the thermal energywithin the hot gases to the cooking surface. The hot gases are caused toflow in one direction lengthwise of the cooking surface through a seriesof adjacent inverted V-shaped gastight channels and then enter intoconnecting adjacent V-shaped channels which alternate with said invertedV-shaped channels and conduct the gases in the opposite direction. Saidchannels are composed of heatconductive materials. The passage throughthe channels promotes a turbulent flow of the hot gases which increasesthe efficiency of heat transfer and the flow of hot gases in oppositedirections results in a balancing of the heat output across the surfaceof the grille by balancing the high temperature at the input end withthe relatively low temperature gas at the output end.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view, partiallybroken away, of a liquid fuel-fired cooking apparatus according to thepresent invention; FIG. 2 is a sectional view in elevation taken in aplane passing through line 22 of FIG. 1; FIG. 3 is a sectional view inelevation taken in a plane passing through line 33 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of thedrawing, there is illustrated a cooking apparatus according to thepresent invention comprising a liquid fuel-fired burner in combinationwith a grille housing.

The liquid fuel burner shown and designated generally as 10 contains aliquid fuel combustor ll of the same type as that described in US Pat.No. 3,408,999. Combustor 11 is centered on a rigid perforated plate 12located at the upstream end of a rectangular combustion chamber 13 andis connected to an external source of liquid fuel and combustion airunder pressure, neither of which are shown in the drawing. Sprayedliquid fuel and air, in addition to excess combustion air passingthrough the perforated plate 12, are blended and caused to burn withinthe combustion chamber 13 and the combustion gases are caused to flow,at the downstream end of the combustion chamber, into a combustionproducts pipe 14. Combustion chamber shroud l5 incloses the combustionchamber and creates an annular space 16 therebetween. A portion of theair supply is forced through annular space 16 cooling the walls of thecombustion chamber to prevent overheating. A cylindrical shroud 17spaced from and inclosing the combustion products pipe 14 allows theflow of cooling air to pass from the annular space 16 through theannular space 19 around pipe 14. At the downstream end of the combustionproducts pipe 14, the combustion gases and cooling air streams cometogether to produce a mixture of blended gases having a temperaturesignificantly lower than that of the combustion gases. The blended gasespass through a cylindrical inlet connector 19 into the grille housing20.

There is disclosed in FIGS. 1 and 2, a grille housing designatedgenerally as 20, rectangular in outline, having a top wall 21 or cookingsurface of a heatconductive material, an opposed bottom wall 22 spacedfrom said top wall and a peripheral side wall 23 between said top andbottom walls defining a hollow chamber 24. A layer of insulation 25covers the base of the chamber and a metal spacer plate 26 rigidlysecured to said peripheral side walls divides the chamber into a lowerportion which contains the layer of insulation and a top portion, thehot gas chamber designated generally as 35, which contains the hot gasdistribution system. A row of similarly positioned angle irons withinhot gas chamber 35 welded to the underside of top wall 21 and the topside of the spacer plate 26 divide the top portion of the chamber 24 ina series of alternating V- shaped 27 and inverted V-shaped 28 gas-tightchannels that alternate across the width of the chamber with eachchannel extending lengthwise of the chamber. The angle irons employedfor this purpose have side walls equal in size and have an includedangle between said side wall of approximately It is preferred that thebase of each channel be not more than 2 inches in width.

The hot gas blend from the burner passes through the cylindrical inletconnector 19 into a rectangular inlet manifold 29 which extendstransversely of the chamber 24 at the rear of the cooking apparatus 20.Apertures 30 located in the inlet manifold 29 provide an opening intoeach of the inverted V-shaped channels 28 allowing the hot gas to flowinto and pass as separate streams along each channel 28 toward the frontof the grille housing. At this point, each hot gas stream flows from thedownstream end of each channel 28 into the next adjacent V-shapedchannel 27 through openings 31 in their respective common walls and thenflows in the opposite direction down each channel 27 toward the back ofthe grille housing. The combustion gas streams exit from each channel 27into a common exhaust manifold 32 located above the inlet manifold andthen pass out as waste gas through an exhaust pipe 34. Undersized exitports 33 in the wall of the exhaust manifold communicate with each ofthe channels 27 allowing the gas to exit while maintaining a slight backpressure within the channels which aids in promoting turbulence withineach gas stream.

In operation, liquid fuel, such as kerosene or gasoline, and combustionair, are delivered to the combuster 11 under pressure and caused to burnwithin the combustion chamber 13. The temperature of the combustiongases as they exit from the combustion chamber are of the order of 900F.to l,800F. Excess air is caused to flow through the annular spaces 16and 18 cooling the walls of the combustion chamber 13 and the walls ofthe pipe 14, respectively. At the downstream end of the combustionproducts pipe 14, the combustion gases join and blend with the coolinggases producing a gas mixture that passes through the cylindrical inletconnector 18 at temperatures of about 300F. to l,000F. The hot gasmixture from the inlet connector 19 flows into the inlet manifold 29and, in turn, via apertures 30 into each of the inverted V- shapedchannels 28. The hot gas streams proceed down each channel 28 and at thedownstream end pass through openings 31 into the connecting andadjoining V-shaped channel 27. The gas streams exit from each channel 27via exit ports 33 into the exhaust manifold and then flow to theatmosphere via exhaust pipe 34. The temperature of the gases leaving theexhaust pipe range from 200F to 400F.

It is to be noted that the hot gas circulation beneath the top wall 21(cooking plate) is such that the gases do not contact the top wall whenat their highest temperature but flow through the inverted V-shapedchannels 28 isolated from the underside of the top wall. Some of theheat energy from the gas is transferred to the conductive side walls ofchannels 27 and 28 so that the temperature of the gas streams declinesas each stream continues down its respective channel 28. On their returnpath through channels 27, the hot gas streams, now reduced intemperature, are now in direct contact with the underside of the topwall and transfer a substantial portion of their thermal energy to saidwall. The net result ofthe gas flow, first in one direction and aseparate flow in the opposite direction, both flows being in heatconductive relationship, is to balance the heat energy transmitted orapplied to the top wall on the cooking surface. The relatively narrowsize of the channels in combination with the undersized exit ports 33entering the exhaust manifold contribute to a slight back pressurewithin each of the channels which promotes turbulence within each of thegas streams. A turbulent gas stream results in a highly efficienttransfer of thermal energy from the hot gas medium to the conductive topwall 21. A system, as described herein, permits the use of liquid-fuelburners which heretofore had been considered to produce temperatures toohigh for conventional cooking and which are notoriously inefficient bothin terms of heat exchange and ability to provide a uniformly heatedsurface.

I claim: 1. A cooking apparatus comprising a housing having spacedopposed top and bottom walls and an encompassing peripheral side wallextending therebetween to define a hot gas chamber with the surface ofthe top wall serving as a cooking surface to transfer heat from said hotgas chamber to an article of food to be cooked; gas inlet means in saidhousing to permit introduction of hot gases into said hot gas chamber;

combustor means cooperating with said gas inlet means generating hotgases which enter said hot gas chamber via said gas inlet means toprovide heat for cooking;

gas distribution means. within said hot gas chamber communicating withsaid gas inlet means to conduct said hot gases in a plurality ofseparate, parallel and substantially equal streams in a first directionlongitudinally within said chamber and continuing in a second directionopposite to said first direction, said streams in said first directionbeing in heat conducting relationship with said streams in said seconddirection and said streams in said second direction being in heatconducting relationship with said top wall, said streams beingsufficient in number to provide even heat distribution in the transversedirection;

gas outlet means in said housing to receive said gases after completionof travel in said second direction beneath said top wall to dischargesaid gas from said chamber.

2. A cooking apparatus according to claim 1 wherein said gasdistribution means comprises a plurality of alternating V-shaped andinverted V-shaped gas-tight channels which extend lengthwise of saidchamber, each of said inverted V-shaped channels connecting with saidgas inlet means at one end and connecting with said V-shaped channels atthe opposite end whereby the hot gases pass from said inlet means intoeach of the inverted V-shaped channels through which they flow in onedirection and pass into the V-shaped channel flowing in the oppositedirection and finally leaving the cooking apparatus through said gasoutlet means.

3. A cooking apparatus according to claim 2 wherein said side walls ofsaid channels are heat conductive.

4. A cooking apparatus according to claim 3 wherein the apex of theangle formed by the side walls of said triangular channel isapproximately 5. A cooking apparatus according to claim 4 wherein saidcombustor means is a liquid fuel burning combustor.

6. A cooking apparatus according to claim 5 wherein said housing is ofgenerally rectangular shape.

7. A cooking apparatus according to claim 6 wherein the connectionbetween said V-shaped channel and said gas outlet means is undersized toproduce back pressure and promote turbulence in said hot gas streams.

1. A Cooking apparatus comprising a housing having spaced opposed topand bottom walls and an encompassing peripheral side wall extendingtherebetween to define a hot gas chamber with the surface of the topwall serving as a cooking surface to transfer heat from said hot gaschamber to an article of food to be cooked; gas inlet means in saidhousing to permit introduction of hot gases into said hot gas chamber;combustor means cooperating with said gas inlet means generating hotgases which enter said hot gas chamber via said gas inlet means toprovide heat for cooking; gas distribution means within said hot gaschamber communicating with said gas inlet means to conduct said hotgases in a plurality of separate, parallel and substantially equalstreams in a first direction longitudinally within said chamber andcontinuing in a second direction opposite to said first direction, saidstreams in said first direction being in heat conducting relationshipwith said streams in said second direction and said streams in saidsecond direction being in heat conducting relationship with said topwall, said streams being sufficient in number to provide even heatdistribution in the transverse direction; gas outlet means in saidhousing to receive said gases after completion of travel in said seconddirection beneath said top wall to discharge said gas from said chamber.2. A cooking apparatus according to claim 1 wherein said gasdistribution means comprises a plurality of alternating V-shaped andinverted V-shaped gas-tight channels which extend lengthwise of saidchamber, each of said inverted V-shaped channels connecting with saidgas inlet means at one end and connecting with said V-shaped channels atthe opposite end whereby the hot gases pass from said inlet means intoeach of the inverted V-shaped channels through which they flow in onedirection and pass into the V-shaped channel flowing in the oppositedirection and finally leaving the cooking apparatus through said gasoutlet means.
 3. A cooking apparatus according to claim 2 wherein saidside walls of said channels are heat conductive.
 4. A cooking apparatusaccording to claim 3 wherein the apex of the angle formed by the sidewalls of said triangular channel is approximately 90*.
 5. A cookingapparatus according to claim 4 wherein said combustor means is a liquidfuel burning combustor.
 6. A cooking apparatus according to claim 5wherein said housing is of generally rectangular shape.
 7. A cookingapparatus according to claim 6 wherein the connection between saidV-shaped channel and said gas outlet means is undersized to produce backpressure and promote turbulence in said hot gas streams.